Bring water to a lively simmer in a saucepan (for a double boiler).

In a saute pan, cook the garlic in the olive oil over medium heat, stirring, until the garlic turns very pale gold.

Set the pan over the simmering water and add anchovies. Stir and mash them against the pan with the back of a wooden spoon until they begin dissolving into a paste. Put the pan back on the burner over medium heat and cook for about 30 seconds or less, stirring constantly.

Add tomatoes, salt, and a few grindings of pepper. Simmer gently but steadily 20 to 25 minutes, stirring from time to time, until the oil floats free from the tomatoes. Toss with hot drained pasta, add parsley, toss once more, and serve immediately.